Television program recording devices such as videocassette recorders (VCRs) have become increasingly popular for recording television programs. As is well known, the "record button" on a VCR can be activated at any time to record a television program being received. Typically, VCRs also include an infrared remote control which may be used for remote activation of the record button, or any other button, to facilitate use of the VCR. As is also well known, many present day VCRs are "programmable" so that a user can set a future time and channel for unattended recording. Such programmable VCRs typically may be programmed with up to fourteen or more "events" so that multiple TV programs may be set for unattended recording.
As is well known to those having skill in the VCR art, the data for events to be recorded is typically stored in the VCR in an "event timer". The event timer is typically a nonvolatile memory so that the contents thereof are not erased if power to the VCR is interrupted, although volatile memories may also be used. The event timer typically includes only that information necessary for controlling the VCR. To set a VCR for recording, "time" and "channel" information must be provided for each event. The "time" information may comprise an indication of a start date and start time (often provided in terms of an actual date and time or in the form of a time from beginning of the year), and an indication of a stop time (in the same form as the start time, or in the form of a program duration from the start time) for each of the events which are to be recorded.
In an effort to simplify user selection of desired TV programs to be viewed and/or recorded, "on-line" television program guides have also been developed and marketed. An on-line program guide is typically broadcast over a satellite or cable system, and the received TV program schedule information is stored in a satellite receiver, cable TV decoder or other unit. An on-line system eliminates paper TV guides, which are difficult to distribute and often are inaccurate because of last minute changes.
A particularly effective system for on-line transmission and reception of television program schedule information is described in U.S. Pat. No. 5,038,211 to Hallenbeck entitled Method and Apparatus for Transmitting and Receiving Television Program Information, which is assigned to the assignee of the present invention, the disclosure of which is hereby incorporated herein by reference. In the Hallenbeck patent, a commercially viable on-line television program information system is provided which extracts from a broadcast datastream only that program information which meets predetermined selection criteria store in the system.
Another example of an on-line TV program schedule system is described in U.S. Pat. No. 4,751,578 to Reiter et al. entitled System for Electronically Controllably Viewing on a Television Updateable Television Programming Information. This patent describes a system for viewing on a television, updateable television programming information, and for permitting the viewer to perform searches on information so as to display subsets of the information desired by the viewer. Yet another example of an on-line TV program schedule system is described in U.S. Pat. No. 4,706,121 to Young entitled TV Schedule System and Process. This patent describes a system for allowing user selection of broadcast programs from schedule information. The schedule information for the selected programs is stored in a memory and is used by the data processor to control a programmable TV tuner.
Attempts have also been made to provide a system for controlling a VCR based on user selected programs from an on-line scheduling system. For example, the aforementioned Young '121 patent describes a system in which user selection criteria are used by a data processor to select programs from the schedule information, and the schedule information is then used to control a VCR for unattended recording of the selected programs. In particular, according to this patent, the schedule information for the selected user programs is stored. The system is connected to the remote control facilities of the VCR, so that at the appropriate time it can supply power to the VCR, start recording and stop recording via the remote control. The VCR may be turned on and off at all appropriate times to record all desired programs. Alternatively, the VCR may be left on all the time and recording may be activated and deactivated via the VCR's "pause" line by remote control.
The above described system for controlling unattended recording by a VCR from an on-line program schedule system provides flexibility for recording. For example, the system may be configured so that the VCR is activated only if the TV is not on at the appropriate time. Moreover, since an on-line scheduling system typically includes classifications of programs by type, an entire series of programs may be designated for recording by merely selecting one program in the series. Also, if the on-line schedule changes, the user selection criteria may be applied to the updated schedule data and the VCR may be activated based upon the new schedule times. In other words, VCR activation is tied to a selected show, or series of shows, regardless of when this show is broadcast.
Notwithstanding the advantage of controlling a VCR from an on-line schedule system, prior systems have not been commercially viable because prior systems required that the program schedule information be stored in a nonvolatile memory so that the VCR could be activated even if power was momentarily lost at the on-line television program schedule system. For example, in the system of the aforesaid '121 patent, the stored TV program schedule listings must be periodically searched against the user's selection criteria in order to determine when the VCR is to be activated. If a power interruption takes place and the listings are lost, the VCR will no longer be activated at the appropriate time and the opportunity to record the program will be irretrievably lost. This undesirable feature could be eliminated by storing the TV program schedule listings in nonvolatile memory. Unfortunately, a nonvolatile memory large enough to store a useful quantity of television program scheduling information is prohibitively expensive and would preclude commercial viability.
In conclusion, on-line TV schedule information systems which provide unattended recording have been faced with two alternatives, neither of which is commercially satisfactory. The system could include a large nonvolatile memory (also referred to as "static RAM") for storing the television program scheduling information, making the system prohibitively expensive. Alternatively, the schedule information could be stored in volatile memory (also referred to as "dynamic RAM"), which means that the recording times will be permanently lost if power is momentarily interrupted. Either alternative precludes a commercially viable system.